JP6158019B2 - Axial turbine generator - Google Patents

Description

  The present invention relates to an axial flow turbine power generation in which loss of blade efficiency is minimized.

In recent years, various power generation methods such as wind power generation and water current power generation have been proposed as clean energy sources that do not emit greenhouse gases during power generation. Current generation using ocean current energy, such as the Kuroshio Current, is one of them, and research and development is actively conducted. The power generation output of the axial turbine generator used for ocean current power generation is expressed by the product of the shaft end output of the runner that converts water kinetic energy into rotational energy and the conversion efficiency. The shaft end output is expressed by the following equation. When a blade with high blade efficiency and large diameter is used, a large output can be obtained.
Shaft end output = (1/2) × density × (flow velocity) ³ × blade efficiency × π × (blade diameter / 2) ²

  The blade efficiency has a theoretical limit (16/27 = 0.5925) called the Betz limit. Actually, (1) loss due to the wake of the blade, (2) loss due to the resistance of the blade cross section, and (3) loss due to the blade tip vortex, the blade efficiency becomes about 0.5.

  Among (1) to (3), (1) the loss due to the wing wake can be suppressed by reducing the rotational torque (increasing the rotational speed) from the angular momentum conservation law. On the other hand, (2) the loss due to the resistance of the blade cross section tends to increase as the rotational speed increases and the drag acting on the blade increases. Thus, since (1) and (2) conflict, it is difficult to make them compatible. However, (3) can be reduced by paying attention to the shape of the blade tip and the trailing edge. Therefore, for wind turbine blades, a method for reducing blade efficiency loss by changing the blade tip shape and a method for reducing blade efficiency loss by attaching a winglet have been proposed.

JP 2012-92660 A JP 2012-180770 A

However, in addition to the fact that the physical properties of water and air are significantly different from each other, the operating conditions are also completely different, and therefore the blade efficiency loss reduction measures in these wind turbines cannot be directly applied to ocean current power generation.
The problem to be solved by the present invention is to provide an axial-flow turbine generator that improves power generation efficiency by minimizing blade efficiency loss in the runner.

An axial-flow turbine generator according to an embodiment includes a generator, a turbine blade including a runner that converts kinetic energy of the water stream into rotational energy and generates a driving force of the generator, and a driving force generated by the runner. And the runner is configured such that the chord length is an optimum value of the chord length at each radial position from the rotation center of the turbine blade, which is obtained by a blade element momentum theory. And the chord length at each radial position from the rotation center of the turbine blade, the chord length being determined by the blade element momentum theory. Do and a second wing region configured to be smaller than the optimum value of Ri, the start position of the second wing region, the distance R from the rotational center of the turbine blade to the blade tip of the runner In contrast, from 0.75R to 0.90R And wherein the 囲Nia Rukoto.

It is a schematic block diagram of the axial-flow water turbine generator concerning a 1st embodiment. It is a schematic structure figure showing the structure of the axial flow turbine power generator concerning a 1st embodiment. It is a top view which shows roughly the runner of 1st Embodiment. It is AA sectional drawing in the runner of FIG. It is a top view which shows the conventional runner schematically. It is a top view which shows the runner of 2nd Embodiment schematically. It is a top view which shows roughly the runner of 3rd Embodiment. It is a top view which shows the runner of 4th Embodiment schematically. It is AA sectional drawing in the runner of FIG. It is a top view which shows the runner of 5th Embodiment schematically. It is a top view which shows the runner of 6th Embodiment schematically. It is a side view which shows the runner of 6th Embodiment schematically. It is a perspective view which shows roughly an example of the baffle plate of 6th Embodiment. It is a front view which shows the runner of 7th Embodiment schematically. It is a side view which shows roughly the runner of 7th Embodiment.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In each figure, components having common functions are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing the axial-flow turbine generators 10 and 20 according to the first embodiment. The axial-flow turbine generators 10 and 20 of this embodiment are propeller-type ocean current power generation (or tidal current power generation) systems installed in the sea 14 and are used, for example, as a pair as shown in FIG. The axial-flow turbine generators 10 and 20 are connected to each other by a connecting member 11 and are anchored (moored) to a seabed 13 having a depth of 200 m or more via a mooring rope 12.

  FIG. 2 is a schematic configuration diagram showing the structure of the axial-flow turbine generators 10 and 20 according to the first embodiment. As shown in FIG. 2, each of the pair of axial water turbine generators 10 and 20 includes an inner cylinder 2, a plurality of runners 3, and a boss 4 that supports the runner 3. The inner cylinder 2, the runner 3, and the boss 4 are configured using a material having high corrosion resistance against seawater or a material coated with a paint having high corrosion resistance.

  The inner cylinder 2 has a watertight structure. As shown in FIG. 2, the inner cylinder 2 contains (accommodates) a generator 5, a transmission mechanism 6 b, and the like that are connected to the rotary shaft 6. The inner cylinder 2 has a predetermined buoyancy. Here, the runner 3 included in each of the pair of axial water turbine apparatuses 10 and 20 rotates in the reverse direction and generates an equivalent thrust. Therefore, the relative positions of the axial water turbine apparatuses 10 and 20 are maintained almost unchanged.

  As shown in FIG. 2, the boss 4 has a function as a support portion that supports the base end side of the runner 3. Further, the boss 4 has a watertight structure like the inner cylinder 2, and a rotating shaft 6 extends through the center of the boss 4. One end portion side of the rotating shaft 6 is connected to the speed change mechanism 6b in the inner cylinder 2, and the other end portion side of the rotating shaft 6 is fixed to the boss 4 body via the hub 6a. That is, the runner 3 is integrally fixed to the rotary shaft 6 at the base end side via the boss 4 (hub 6a), and rotates together with the rotary shaft 6 (boss 4) when receiving a water flow. .

  The power (driving force) of the rotating shaft 6 is transmitted to the generator 5 in the inner cylinder 2. Specifically, the rotation of the rotating shaft 6 is decelerated or increased by the speed change mechanism 6 b and is transmitted to the generator 5 via the transmission shaft 6 c between the speed change mechanism 6 b and the generator 5.

  The runner 3 is a horizontal axis lift type runner, and is provided, for example, two or three for each of the axial-flow turbine generators 10 and 20. For example, when there are three runners 3, the individual runners 3 are respectively fixed at 120 ° intervals around the axis of the boss 4 (rotating shaft 6) to constitute turbine blades. Each runner 3 has a shape in which each of the pressure surface (positive pressure surface) and the suction surface are aligned in a certain direction so that the rotation force of the rotating shaft 6 rotating in a certain direction can be obtained from each of the runners 3. Is formed.

  In the turbine blade, the runner 3 converts the kinetic energy obtained from the water current (sea current) F1 into rotational energy, as shown in FIG. On the other hand, the rotating shaft 6 that rotates together with the runner 3 transmits the converted rotational energy to the generator 5 in the inner cylinder 2 via the transmission mechanism 6b and the transmission shaft 6c. Electric power is generated using this rotational energy.

  Next, a characteristic configuration of the runner 3 will be described with reference to FIGS. 3 and 4. FIG. 3 is a plan view schematically showing the runner 3 according to the first embodiment, and FIG. 4 is a cross-sectional view taken along line AA of the runner 3 shown in FIG. In the runner 3 of the first embodiment shown in FIG. 3, the distance from the rotation center 30 of the turbine blade to the blade tip 31 is R. As shown in FIG. 4, the runner 3 has a blade cross-sectional shape that is streamlined. In the runner shown in FIG. 4, reference numeral 32 denotes a leading edge, reference numeral 33 denotes a trailing edge, reference numeral 34 denotes a suction surface, and reference numeral 35 denotes a pressure surface. Although the runner 3 is shown as a solid structure in FIG. 4, the runner 3 may be formed in a hollow shape in order to reduce the weight.

The runner 3 of the first embodiment is located on the blade base end (blade root) side, and the chord length C ₁ (r) at the radial position r from the rotation center 30 of the turbine blade is calculated by the blade element momentum theory. A first blade region 3a configured to have an optimum value of the chord length at each required radial position r, and located on the blade tip 31 side of the first blade region, the chord length C ₂ ( r) includes a second blade region 3b configured to be smaller than the optimum value of the chord length at each radial position r determined by the blade element momentum theory. In the runner 3, in the first blade region, C ₁ (r) decreases at a substantially constant reduction rate dC ₁ (r) / dr from the blade base end side toward the blade tip 31, and the second blade region 3b. The chord length reduction rate dC ₂ (r) / dr is larger than dC ₁ (r) / dr from the start position R1 of C1, and C ₂ (r) decreases at a substantially constant dC ₂ (r) / dr. It is structured into a shape.

  Here, a conventional runner 307 will be described with reference to FIG. 5 for comparison. FIG. 5 is a plan view schematically showing a conventional runner 307. The conventional runner 307 shown in FIG. 5 has a blade cross section formed in a streamlined manner. In addition, the chord length C (r) at each radial position r of the runner 307 is configured to be an optimum value of the chord length at each radial position r obtained by the blade element momentum theory, and its blade proximal end The chord length is reduced at a substantially constant reduction rate from the part side toward the blade tip 31.

  As a factor of blade efficiency loss in the turbine blade constituted by the runner 307, there is generation of a blade tip vortex. In the vicinity of the blade tip 31, a flow (down) from the pressure surface 35 side to the suction surface 34 side occurs due to the pressure difference between the suction surface 34 and the pressure surface 35, thereby generating blade tip vortices. This blade tip vortex locally changes the flow direction of the water flow (ocean current) F1 in the vicinity of the runner 307, so that induction resistance is generated and blade efficiency loss occurs. The Karman vortex generated behind the trailing edge 33 in the vicinity of the blade tip 31 is also a factor of the blade efficiency loss, and the mutual interference between the Karman vortex and the blade tip vortex increases the blade efficiency loss.

On the other hand, in the runner 3 of the first embodiment shown in FIG. 3, by maintaining the optimum value of the chord length in the first blade region 3a, the blade efficiency in the first blade region 3a is maintained. In the second blade region 3b, C ₂ (r) is made smaller than the optimum value of the chord length, thereby reducing the lift generated by the blade element and reducing the blade load. Since the blade load is equal to the pressure difference between the pressure surface 35 and the suction surface 34, the generation of blade tip vortices is suppressed.

  The distance R1 from the rotation center 30 to the start position of the second blade region 3b is preferably such that R1 / R is in the range of 0.75 to 0.9, and is in the range of 0.85 to 0.9. Is preferred. Thereby, blade efficiency loss due to generation of blade tip vortices can be reduced while maintaining blade efficiency in the first blade region 3a.

Further, the runner 3 is configured in a bent line shape in which the leading edge 32 and the trailing edge 33 in the second blade region 3b are bent stepwise toward the tip, or a curved shape that is sunk toward the blade tip 31, and dC ₂ ( It is preferable that r) / dr increase stepwise or gradually from the start position R1 of the second blade region 3b toward the blade tip 31 side. As a result, the lift generated by the blade element in the second blade region 3b is extremely reduced, and the generation of blade tip vortices is further suppressed.

  As described above, in the axial-flow turbine generators 10 and 20 according to the first embodiment, the blade efficiency loss is reduced by suppressing the generation of the blade tip vortex in the runner 3. Furthermore, since generation | occurrence | production of a blade tip vortex is suppressed, the mutual interference of a blade tip vortex and a Karman vortex is suppressed and blade efficiency loss is suppressed more. Therefore, the power generation efficiency in the axial flow turbine power generators 10 and 20 can be improved.

  Next, axial flow turbine power generators according to second to seventh embodiments will be described with reference to the drawings. The axial flow turbine power generators according to the second to seventh embodiments are the same as those of the first embodiment except that the shape of the runner 3 is different in the axial flow turbine power generators 10 and 20 of the first embodiment. It is the same as that of the axial flow turbine power generators 10 and 20. Therefore, the runners in the respective embodiments will be described in detail, and the other configurations are the same as those in the first embodiment, and thus redundant description will be omitted. Regarding the runner, the same components as those of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

(Second Embodiment)
A runner 301 according to the second embodiment will be described with reference to FIG. FIG. 6 is a schematic configuration diagram of a runner 301 according to the second embodiment. The runner 301 shown in FIG. 6 is formed by connecting the trailing edge 33 linearly at all radial positions in the second blade region 3b, and the leading edge 32 approaches the trailing edge 33. C ₂ (r) is configured to decrease toward the blade tip 31. That is, the runner 301 has a planar shape in which the trailing edge 33 is substantially linear from the start position R2 of the second blade region 3b toward the blade tip 31, and the leading edge 32 is centered on the inside of the blade. Or it is formed as the shape which draws the arc of an ellipse. In the runner 301, the distance R2 from the rotation center 30 of the turbine blade to the start position of the second blade region 3b is preferably larger than R1 in the first embodiment, and R2 / R is 0.85 to 0. More preferably, it is in the range of .9. Thereby, blade efficiency loss due to generation of blade tip vortices can be reduced while maintaining blade efficiency in the first blade region 3a.

In the second embodiment, as in the first embodiment, C ₂ (r) is made smaller than the optimum value of the chord length at each radial position r, thereby suppressing the generation of blade tip vortices. Is done. Further, since the runner 301 has a blade cross-sectional shape that is sharp at the trailing edge 33 side, the runner 301 is formed so that the leading edge 32 approaches the trailing edge 33 in the second blade region 3 b of the runner 301. Thus, the blade cross-sectional shape on the trailing edge 33 side is maintained as it is, and the moldability is improved.

(Third embodiment)
Next, a runner 302 according to the third embodiment will be described with reference to FIG. FIG. 7 is a schematic configuration diagram of the runner 302 according to the third embodiment. The runner 302 shown in FIG. 7 is formed by connecting the leading edge 32 linearly at all radial positions in the second blade region 3b, and the trailing edge 33 approaches the leading edge 32 so that C ₂ (r ) Decreases toward the blade tip 31. That is, the runner 302 has a planar shape that is substantially straight from the start position R3 of the second blade region 3b toward the blade tip 31 and has a rear edge 33 centered on the inside of the blade. It is formed as a shape that draws an arc of a circle or an ellipse. In the runner 302, the distance R3 from the rotation center 30 of the turbine blade to the start position of the second blade region 3b can be equal to or larger than R1 in the first embodiment, and R3 / R is more preferably in the range of 0.85 to 0.9. Thereby, blade efficiency loss due to generation of blade tip vortices can be reduced while maintaining blade efficiency in the first blade region 3a.

As in the first embodiment, the runner 302 of the third embodiment is such that C ₂ (r) in the second blade region 3b is more than the optimum value of the chord length obtained by the blade element momentum theory. It has been made smaller. Therefore, generation of blade tip vortices in the vicinity of the blade tip 31 of the runner 302 is suppressed. Further, since the runner 302 is configured such that the trailing edge 33 approaches the leading edge 32, the generation center of the blade tip vortex is moved away from the upstream side of the water flow. Therefore, the generation center of the blade tip vortex and the generation center of the Karman vortex are moved away, and mutual interference between the blade tip vortex and the Karman vortex is suppressed. Therefore, it is possible to greatly reduce the blade efficiency loss. Therefore, according to this embodiment, the power generation efficiency in the axial flow turbine power generators 10 and 20 can be improved.

(Fourth embodiment)
Next, a runner 303 according to a fourth embodiment will be described with reference to FIGS. FIG. 8 is a plan view schematically showing a runner 303 according to the fourth embodiment. FIG. 9 is a cross-sectional view taken along line AA at an arbitrary radial position r of the runner 303 shown in FIG.

  In the runner 303 shown in FIG. 8, the distance from the rotation center 30 of the turbine blade to the blade tip 31 is R, and the blade cross-sectional shape is streamlined. The chord length C (r) at each radial position r from the rotation center 30 of the turbine blade of the runner 303 is configured to be an optimum value of the chord length at each radial position r determined by the blade element momentum theory. The chord length C (r) decreases at a substantially constant decreasing rate from the blade base end side toward the blade tip 31. Although the runner 303 is shown as a solid structure in FIG. 9, the runner 303 may be formed in a hollow shape in order to reduce the weight.

  As shown in FIG. 9, the runner 303 of the present embodiment has an asymmetric edge shape on the trailing edge 33 side of the blade element at each radial position r. In the runner 303, the edge shape functions as a vortex suppressing structure that suppresses the generation of vortices near the blade tip 31 of the runner 303. The edge shape includes a blade end face edge surface 36 formed on the trailing edge 33 side of the runner 303 so that the suction surface 34 is longer than the pressure surface 35. The edge surface 36 is formed such that the tangent t of the negative pressure surface 34 and the edge surface 36 form an acute angle at the intersection of the edge surface 36 and the negative pressure surface 34. In the runner 303, the edge surface 36 may be formed at all radial positions of the turbine blades of the runner 303, or may be formed at some radial positions. In order to suppress the interference between the Karman vortex and the blade tip vortex, the edge surface 36 is formed such that the distance R4 from the rotation center of the turbine blade is in a range where R4 / R is 0.3 to 1.0. preferable. The edge surface 36 is preferably formed so that the angle α between the tangent t and the edge surface 36 is 30 to 60 ° from the viewpoint of suppressing the generation of Karman vortices.

  In the runner 303 of the present embodiment, the trailing edge 33 has an asymmetric edge shape, so that generation of Karman vortex from the trailing edge 33 is suppressed, and blade efficiency loss due to Karman vortex is suppressed. Furthermore, since the generation of Karman vortices is suppressed, blade efficiency loss due to mutual interference between Karman vortices and blade tip vortices is also reduced.

  The planar shape of the runner 303 may be the same as that of the first to third embodiments, and the blade efficiency loss can be greatly reduced. Therefore, according to this embodiment, it is possible to improve the power generation efficiency in the axial-flow turbine power generators 10 and 20.

(Fifth embodiment)
Next, a runner 304 according to a fifth embodiment will be described with reference to FIG. FIG. 10 is a plan view schematically showing a runner 304 according to the fifth embodiment. In the runner 304 shown in FIG. 10, the distance from the rotation center 30 of the turbine blade to the blade tip 31 is R, and the blade cross-sectional shape is streamlined. The chord length C (r) at each radial position r from the rotation center 30 of the turbine blade of the runner 304 is configured to be an optimum value of the chord length at each radial position r determined by the blade element momentum theory. The chord length C (r) decreases at a substantially constant reduction rate from the blade base end portion toward the blade tip 31. The runner 304 has a bent portion 37 near the blade tip 31. The bent portion 37 functions as a vortex suppressing structure that suppresses the generation of vortices in the vicinity of the blade tip 31 of the runner 304.

  The bent portion 37 is formed, for example, by bending the vicinity of the blade tip 31 of the conventional runner 307 in the upstream direction of the water flow. The distance R5 from the rotation center 30 to the start position of the bent portion 37 is preferably such that R5 / R is in the range of 0.75 to 0.9, and more preferably in the range of 0.85 to 0.9. . Thereby, since blowing down can be suppressed, the electric power generation efficiency of a turbine blade can be improved. Further, the chord length in the bent portion 37 may be substantially constant from the starting position of the bent portion 37 to the blade tip 31 or may be decreased.

  Further, from the viewpoint of suppressing the generation of the blade tip vortex, the bending angle β is preferably 5 to 40 °. Here, the bend angle β is a line connecting the center of the chord line in the cross section of the blade base end portion and the center of the chord line in the cross section of the start position of the bend portion 37 and the cross section of the start position of the bend portion 37. It indicates the acute angle among the angles formed by the line connecting the center of the chord line and the center of the chord line in the cross section of the blade tip 31.

  The runner 304 according to the fifth embodiment has the bent portion 37, so that the generation position of the blade tip vortex can be moved to the upstream side of the water flow. Therefore, mutual interference between the blade tip vortex and the Karman vortex is suppressed, and blade efficiency loss is reduced. Moreover, since the bent part 37 suppresses blowing down, generation | occurrence | production of the induction resistance by blowing down is suppressed and blade efficiency loss is reduced.

  Note that the planar shape of the runner 304 may be the same as that of the first to third embodiments, which can significantly reduce blade efficiency loss. Therefore, according to this embodiment, it is possible to improve the power generation efficiency in the axial-flow turbine power generators 10 and 20.

(Sixth embodiment)
Next, a runner 305 according to the sixth embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a plan view schematically showing a runner 305 according to the sixth embodiment. FIG. 12 is a side view schematically showing the runner 305 shown in FIG.

  In the runner 305 according to the sixth embodiment, the distance from the rotation center 30 of the turbine blade to the blade tip 31 is R, and the blade cross-sectional shape is streamlined. The chord length C (r) at each radial position r from the rotation center 30 of the turbine blade of the runner 305 is configured to be an optimum value of the chord length at each radial position r determined by the blade element momentum theory. The chord length C (r) decreases at a substantially constant reduction rate from the blade base end portion toward the blade tip 31.

  A runner 305 according to the sixth embodiment is provided with a rectifying plate 38 that suppresses down-flow at the blade tip 31. The current plate 38 functions as a vortex suppressing structure that suppresses the generation of vortices in the vicinity of the blade tip 31 of the runner 305. The rectifying plate 38 has a plate shape or a blade shape having an appropriate thickness, and is joined to the blade tip 31 from the outside of the blade tip surface of the runner 305. The rectifying plate 38 is provided to protrude to a predetermined length on the negative pressure surface 34 side and the pressure surface 35 side, on the front edge 32 side and on the rear edge 33 side. Further, for example, in the rectifying plate 38, the plate surface of the rectifying plate 38 at the joining position of the runner 305 and the rectifying plate 38 connects the centers of the respective chord lines in the section of the blade base end of the runner 305 and the blade tip 31. It is provided so as to be substantially orthogonal to the elliptical line. The current plate 38 is formed of the same material as that of the runner 305, for example.

  FIG. 13 is a perspective view schematically showing an example of the current plate 38 in the present embodiment. The shape of the rectifying plate 38 is not particularly limited, but in order to suppress the generation of drag in the rectifying plate 38, it is preferable that the cross-sectional shape is, for example, an airfoil shape having a streamline shape as shown in FIG. In this case, the current plate 38 is provided such that the front edge 381 is positioned in the rotation direction of the runner 305. Further, the vicinity of the trailing edge 382 of the rectifying plate 38 is preferably an asymmetric edge shape in which the negative pressure surface 384 side is longer than the pressure surface 385 side in order to suppress the generation of Karman vortices. The size of the rectifying plate 38 is not particularly limited as long as the size of the rectifying plate 38 can be suppressed, but the length of the blade width line 383 is preferably 2 to 4 times the maximum blade thickness of the runner 305. Thereby, since blowing down can be suppressed, the electric power generation efficiency of a turbine blade can be improved. Note that the wing span line 383 is defined as a line connecting the centers of the chord lines in the cross section of both wing tips of the rectifying plate 38. Further, the rectifying plate 38 is provided so that the center of the blade width line 383 is located on the extension of the line connecting the centers of the chord lines in the cross sections of the blade base end and the blade tip 31 of the runner 305. It is preferable. The thickness and chord length of the rectifying plate 38 can be appropriately designed according to the desired blade efficiency.

  In the runner 305 of the present embodiment, the rectifying plate 38 suppresses the blow-down. Therefore, the generation of induction resistance due to blowing down is suppressed, and blade efficiency loss is reduced. Furthermore, since the rectifying plate 38 is also provided on the pressure surface 35 side, the generation position of the blade tip vortex is moved away to the upstream side of the water flow. Therefore, blade efficiency loss due to mutual interference between the blade tip vortex and the Karman vortex can be suppressed.

  In addition, the planar shape of the runner 305 may be the same as that of the first to third embodiments, which can significantly reduce blade efficiency loss. Therefore, according to this embodiment, it is possible to improve the power generation efficiency in the axial-flow turbine power generators 10 and 20.

(Seventh embodiment)
Next, a runner 306 according to a seventh embodiment will be described with reference to FIGS. 14 and 15.

  FIG. 14 is a plan view schematically showing a runner 306 according to the seventh embodiment. FIG. 15 is a side view schematically showing the runner 306 shown in FIG. Although FIG. 14 illustrates three runners, the number of runners is not limited to this.

  In the runner 306, the distance from the turbine rotation center 30 to the blade tip 31 is R, and the blade cross-sectional shape is streamlined. The chord length C (r) at each radial position r from the rotation center 30 of the turbine blade of the runner 306 is configured to be an optimum value of the chord length at each radial position r determined by the blade element momentum theory. The chord length C (r) decreases at a substantially constant reduction rate from the blade base end portion toward the blade tip 31.

  The runner 306 includes a cylinder 39 that inscribes each blade tip 31. The cylinder 39 functions as a vortex suppressing structure that suppresses the generation of vortices in the vicinity of the blade tip 31 of the runner 306. The cylinder 39 is formed of the same material as that of the runner 306, for example. The thickness in the length direction and the radial direction of the cylinder 39 is not particularly limited as long as it can suppress the downflow in the vicinity of the blade tip 31 of the runner 306, and the axial flow turbine power generators 10 and 20 are not limited thereto. What is necessary is just to design suitably according to it. For example, it is preferable that the thickness of the cylinder 39 in the length direction is substantially the same as or slightly larger than the chord length at the blade tip 31 of the runner 306 from the viewpoint of suppressing down-flow.

  In the runner 306, the cylinder 39 prevents the runner from blowing down in the vicinity of the blade tip 31 of each runner. Therefore, the generation of induction resistance due to blowing down is suppressed, and blade efficiency loss is reduced.

  In addition, the planar shape of the runner 306 may be the same as that of the first to third embodiments, and thereby the blade efficiency loss can be greatly reduced. Thus, according to this embodiment, it is possible to improve the power generation efficiency in the axial-flow turbine generators 10 and 20.

As described above, according to the embodiment described above, it is possible to improve the power generation efficiency in the axial-flow turbine generators 10 and 20 by suppressing the blade efficiency loss.
The

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10,20 ... Axial flow turbine power generator, 3,301-307 ... runner, 3a ... 1st wing | blade area | region, 3b ... 2nd wing | blade area | region, 4 ... boss | hub, 5 ... generator, 6 ... rotating shaft, 6a ... Hub, 6b ... Transmission mechanism, 6c ... Transmission shaft, 7 ... Generator, 11 ... Connecting member, 12 ... Mooring rope, 13 ... Submarine, 14 ... Underwater, 30 ... Rotation center of turbine blade, 31 ... Blade tip, 32, 381 ... Leading edge, 33, 382 ... Trailing edge, 34, 384 ... Suction surface, 35, 385 ... Pressure surface, 36 ... Edge surface, 37 ... Curved part, 38 ... Rectifying plate, 39 ... Cylindrical, 383 ... Blade width line , Α: bend angle, β: edge angle, C, C ₁ , C ₂ ... chord length, R: distance from the rotation center of the turbine blade to the blade tip, R1, R2, R3, R4, R5 ... rotation of the turbine blade Distance from center.

Claims (5)

A generator,
A turbine blade comprising a runner that converts the kinetic energy of the water flow into rotational energy to generate the driving force of the generator;
An axial-flow turbine generator comprising a rotating shaft that transmits the driving force generated by the runner to the generator,
The runner is
A first blade region configured such that the chord length is an optimum value of the chord length at each radial position from the rotation center of the turbine blade, which is obtained by a blade element momentum theory;
It is located on the blade tip side from the first blade region, and the blade chord length is smaller than the optimum value of the chord length at each radial position from the rotation center of the turbine blade determined by the blade element momentum theory. A second wing region configured;
The starting position of the second wing region, with respect to the distance R from the center of rotation of the turbine blade to the blade tip of the runner, the axis running water, characterized in range near Rukoto of 0.75R~0.90R Car power generator. In the second wing regions, with the go blade tip, according to claim 1 Symbol mounting axis running water vehicle power generating device of the leading edge, characterized in that the chord length decreases approaching the trailing edge of the runner. 3. The axial-flow water turbine generator according to claim 1, wherein in the second blade region, the trailing edge of the runner approaches the leading edge and the chord length decreases with going to the blade tip. The axial flow turbine power generator according to any one of claims 1 to 3 , wherein the runner includes a vortex suppressing structure that suppresses generation of vortices in the vicinity of a blade tip of the runner. The vortex suppressing structure has a blade end surface edge surface formed by making the suction surface longer than the pressure surface at the trailing edge of the runner, and the vicinity of the runner blade tip is inclined in the upstream direction of water flow. 5. The axial-flow turbine generator according to claim 4, wherein the power generator is one or more of a bent portion, a rectifying plate provided at a blade tip of the runner, or a cylinder inscribed in the blade tip of the runner.

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